I had thought because light was absorbed and re-emitted but that and scattering ideas are incorrect. See this video for an explanation of why light travels slow

I had thought because light was absorbed and re-emitted but that and scattering ideas are incorrect. See this video for an explanation of why light travels slower through a medium with an index of refraction greater than one. https://youtu.be/CUjt36SD3h8 https://youtu.be/CUjt36SD3h8